1. Field of the Invention
The present invention relates to a thermoplastic packaging comprising at least one inner layer and one outer layer, which is especially suited to contain cosmetic or dermatological compositions and serves to protect the contents from light radiation and from oxidation, while at the same time having a satisfying aesthetic appearance, and a process for the production of the packaging.
2. Discussion of the Background
EP-A-0 204 324 discloses a multilayer pad, the thermoplastic outer layer of which comprises an inorganic filler. However, this filler must have a very small particle size and does not provide a satisfying aesthetic appearance.
FR-A-2 657 048 teaches a process for manufacturing packaging which has a natural-stone external appearance and having a wall which consists of a monolayer thermoplastic matrix which includes at least two fillers of different sizes or particle sizes.
These types of thermoplastic packaging are obtained by means of known shaping processes of the injection-molding type.
Unfortunately, the fillers are not always distributed uniformly in the matrix and are not always present in sufficient quantity to impart a satisfying stone appearance. Indeed, too large a quantity of filler in the material leads to a reduction in the elasticity of the material and can cause the appearance of holes and/or cracks in the wall of the packaging. This leads to increased air permeability of the wall, which can lead to degradation of the contents of the packaging.
Likewise, the presence of particles of large diameter, especially greater than the thickness of the wall, may cause holes and/or cracks. However, to impart a suitable stone appearance, it is necessary to use a large quantity of filler, having a large and varied particle size.
Other techniques for shaping plastics, such as coextrusion or coextrusion/blowing are known for unfilled plastics. These techniques consist in simultaneously extruding several plastics through the same die. They can be used to obtain components whose various materials constituting the inner and outer walls do not mix and remain uniformly distributed. These techniques have the advantage of being able to use two different materials for the inner and outer walls of the packaging.
This technique is especially described in U.S. Pat. No. 4,292 355 for the manufacture of a plastic container, consisting only of a polypropylene layer and a butadiene styrene polymer layer.
Unfortunately, this choice of material does not enable fillers to be added to the materials constituting the outer layer.